From Ohio History Central

During the past two million years, glaciers have shaped and reshaped the surface of Ohio several times. These continental masses of ice affected as much as two-thirds of the state. Moving from the north and northwest, glaciers have scraped and flattened the landscape. Often more than a mile thick, they smoothed existing hills and filled valleys with enormous amounts of rocks, gravel, and smaller particles.

Through these actions, glaciers have had a very important impact on the agriculture of Ohio. Their activity has been felt in two noticeable ways: shaping the ground upon which people work and build, and forming the soils that cover that ground.

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The Glaciers

Continental glaciers are masses of ice, formed from compacted snow, that move across a land surface.One of the most dramatic remains of glaciers in Ohio can be seen at the Glacial Grooves State Memorial on Kelleys Island in Lake Erie. Rocks and gravel embedded in the glacial ice ground away rock leaving scratches and grooves in the bedrock.

Ohio's Terrain

The part of Ohio that was covered by glaciers includes about two-thirds of the northern and western parts of the state. Most of southeastern Ohio was not covered by glaciers.

In glaciated Ohio, the surface of the land usually is fairly level or gently rolling. On the other hand, steep ridges, hills and shaded valleys, characterize unglaciated Ohio. One author has estimated that a 200-acre farm in unglaciated Ohio may have as little as 12 acres of land that a tractor can plow and work.